Anyone know where I can purchase a duel leg/back brace. The point of this is to change the center of gravity to one leg which will lock at 90%. I have been looking around for a while and couldn't find a place to purchase. Also, I tried constructing my own but it is extremely difficult.

I don't believe this is an item that is (commonly) for sale. I assume that you intend to use it for a type of "Matrix" gravity-resistance suspension.
If you have tried and failed to construct your own apparatus, I would suggest that you find someone who is more adept at building such things, and pay him or her to construct it for you. You would be wise to get in contact with an engineer to help you come up a few different design prototype designs. Review them and decide which would best accomodate your needs.